EP 1058383 A3 describes a frequency separating unit with thin-film resonators.
WO 2004/047290 A1 describes a front-end circuit with a frequency separating unit, in which a λ/4 line arranged in a receive path and connected before a band-pass filter is used as a phase shifter.
EP 0 788 182 A2 describes an MWK duplexer (MWK=microwave ceramic) with dielectric resonators, in which a 180° phase shifter has LC elements instead of a λ/4 line.